Difference between visual and normal keyframes
The following cube has a limit location set to (0,0,0) when you move the cube its position in the viewport don't change while the location info in the transform panel shows this change:



this is the case for all constraints they won't change what is displayed on the properties panel while they change the visual properties ( loc, rot, scale)




so you if you keyframe the location you'll store (1.938, 0.411, 1.286) for the current frame
while if you keyframe the visual location you'll store (0, 0, 0)